Stable quark stars beyond neutron stars: Can they account for the missing matter ?

The structure of a spherically symmetric stable dark'star' is discussed, at zero temperature, containing 1) a core of quarks in the deconfined phase and antileptons 2) a shell of hadrons in particular n, p, ? and S- and leptons or antileptons and 3) a shell of hydrogen in the superfluid phase. If the superfluid hydrogen phase goes over into the electromagnetic plasma phase at densities well below one atom / (10 fm)³, as is usually assumed, the hydrogen shell is insignificant for the mass and the radius of the'star'. These quantities are then determined approximatively: mass = 1.8 solar masses and radius = 9.2 km. On the contrary if densities of the order of one atom / (10 fm)³ do form a stable hydrogen superfluid phase, we find a large range of possible masses from 1.8 to 375 solar masses. The radii vary accordingly from 9 to 1200 km.